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Thorium biosorption by a green microalga, Chlorella Vulgaris , was studied in a stirred batch reactor to investigate the effect of initial solution pH, metal ion concentration, biomass dosage, contact time, kinetics, equilibrium and thermodynamics of uptake. The green microalgae showed the highest Th adsorption capacity at 45 °C for the solution with a thorium concentration of 350 mg L −1 and initial pH of 4. The amount of uptake raised from 84 to 104 mg g −1 as the temperature increased from 15 to 45 °C for an initial metal concentration of 75 mg L −1 at pH 4. Transformation Infrared Spectroscopy (FTIR) was employed to characterize the vibrational frequency changes for peaks related to surface functional groups. Also, the scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX) were used to determine the morphological changes and elemental analysis of the biosorbent before and after the sorption process. The Langmuir isotherm was in perfect agreement with the equilibrium empirical data of thorium biosorption and the highest sorption capacity of the Chlorella Vulgaris microalgae was determined as 185.19 mg g −1 . Also, the results of kinetic studies show that the thorium biosorption process follows a pseudo-second-order kinetic model. The negative value of ΔG 0 indicates spontaneity and the positive values of ΔH 0 indicate the endothermic nature of the adsorption process.

Thorium, as an important radioactive element, is widely present in nature, and its accompanying environmental pollution is also serious. Extracellular polymeric substances (EPS) are commonly found on the surface of microbial bodies and have strong adsorption capacity for metal ions. In this study, four methods were used to extract EPS from indigenous bacteria of rare earth tailings and to determine the best extraction method. The extracted EPS was applied to treat Th4+, and the changes in functional groups and composition of EPS were investigated. The results showed that the ultrasonic method was more efficient than other methods. The best removal efficiency was observed at pH 3.5, Th4+ concentration of 20 mg/L, and EPS dosage of 30 mL at 25 °C. After 9 h, the adsorption process reached equilibrium with a maximum removal efficiency of 75.93% and a maximum theoretical adsorption capacity of 25.96 mg/g. The Th4+ removal process was consistent with the Langmuir and Freundlich adsorption isotherms and the kinetic data were consistent with the pseudo-second-order kinetic model, which is mainly based on chemisorption. Amide I and amide II of proteins, C–H from aliphatic, as well as O–H and C = O from carboxylic acid play important roles in the adsorption process.

Ferritin is the main protein of Fe storage in eukaryote and prokaryote cells. It is a large multifunctional, multi‐subunit protein consisting of heavy H and light L subunits. In the field of nuclear toxicology, it has been suggested that some actinide elements, such as thorium and plutonium at oxidation state +IV, have a comparable `biochemistry' to iron at oxidation state +III owing to their very high tendency for hydrolysis and somewhat comparable ionic radii. Therefore, the possible mechanisms of interaction of such actinide elements with the Fe storage protein is a fundamental question of bio‐actinidic chemistry. We recently described the complexation of Pu(IV) and Th(IV) with horse spleen ferritin (composed mainly of L subunits). In this article, we bring another viewpoint to this question by further combining modeling with our previous EXAFS data for Pu(IV) and Th(IV). As a result, the interaction between the L subunits and both actinides appears to be non‐specific but driven only by the density of the presence of Asp and Glu residues on the protein shell. The formation of an oxyhydroxide Th or Pu core has not been observed under the experimental conditions here, nor the interaction of Th or Pu with the ferric oxyhydroxide core. The mechanisms of interaction of thorium and plutonium with Fe storage horse spleen ferritin protein (L subunit) have been described by combining modeling with EXAFS data. The interaction between the L subunits and both actinides appears to be driven by the density of the presence of Asp and Glu residues on the protein shell.

Preceramic human skeletal remains preserved in submerged caves near Tulum in the Mexican state of Quintana Roo, Mexico, reveal conflicting results regarding 14C dating. Here we use U-series techniques for dating a stalagmite overgrowing the pelvis of a human skeleton discovered in the submerged Chan Hol cave. The oldest closed system U/Th age comes from around 21 mm above the pelvis defining the terminus ante quem for the pelvis to 11311±370 y BP. However, the skeleton might be considerable older, probably as old as 13 ky BP as indicated by the speleothem stable isotope data. The Chan Hol individual confirms a late Pleistocene settling of Mesoamerica and represents one of the oldest human osteological remains in America.

The concentrations of uranium, thorium, barium, nickel, strontium and lead in the samples of the tailings and plant species collected from a uranium mill tailings repository in South China were analyzed. Then, the removal capability of a plant for a target element was assessed. It was found that Phragmites australis had the greatest removal capabilities for uranium (820 μg), thorium (103 μg) and lead (1,870 μg). Miscanthus floridulus had the greatest removal capabilities for barium (3,730 μg) and nickel (667 μg), and Parthenocissus quinquefolia had the greatest removal capability for strontium (3,920 μg). In this study, a novel coefficient, termed as phytoremediation factor (PF), was proposed, for the first time, to assess the potential of a plant to be used in phytoremediation of a target element contaminated soil. Phragmites australis has the highest PFs for uranium (16.6), thorium (8.68), barium (10.0) and lead (10.5). Miscanthus floridulus has the highest PF for Ni (25.0). Broussonetia papyrifera and Parthenocissus quinquefolia have the relatively high PFs for strontium (28.1 and 25.4, respectively). On the basis of the definition for a hyperaccumulator, only Cyperus iria and Parthenocissus quinquefolia satisfied the criteria for hyperaccumulator of uranium (36.4 μg/g) and strontium (190 μg/g), and could be the candidates for phytoremediation of uranium and strontium contaminated soils. The results show that the PF has advantage over the hyperaccumulator in reflecting the removal capabilities of a plant for a target element, and is more adequate for assessing the potential of a plant to be used in phytoremediation than conventional method.

The distribution of neodymium, lead, thorium and uranium was investigated in about 100 samples of 12 different species of common, edible and non-edible mushrooms collected in unpolluted areas in the province of Ciudad Real, Central Spain. The quantitative analysis of heavy metals was performed by X-ray fluorescence spectrometry (a simple, accurate and non-destructive method). The concentration of these elements was related to three factors: mushroom specie, life style/substrate and study area. The results reveal considerable amounts of the four metals in all species analyzed as well as significant differences on the capability to accumulate these elements. The maximum absorption of Nd and Pb was found in the ectomycorrhizal Cantharellus cibarius, reaching values of 7.10 and 4.86 μg g⁻¹, respectively. Thorium and uranium were mainly accumulated (3.63 and 4.13 μg g⁻¹, respectively) in Hypholoma fasciculare although it is an epiphyte species, isolated from the mineral particles of soil. The distribution patterns of these metals in sporocarps of different habitats and locations showed no significant differences, except for thorium, mainly accumulated in mushrooms living on wood regarding these living on soil organic matter. The species-specific is therefore the determining factor for accumulation of Nd, Pb, Th and U, more than substrate, in this study.

The effects of different hydroponic conditions (such as concentration of thorium (Th), pH, carbonate, phosphate, organic acids, and cations) on thorium uptake by Brassica juncea var. foliosa were evaluated. The results showed that acidic cultivation solutions enhanced thorium accumulation in the plants. Phosphate and carbonate inhibited thorium accumulation in plants, possibly due to the formation of Th(HPO₄)²⁺, Th(HPO₄)₂, or Th(OH)₃CO₃⁻with Th⁴⁺, which was disadvantageous for thorium uptake in the plants. Organic aids (citric acid, oxalic acid, lactic acid) inhibited thorium accumulation in roots and increased thorium content in the shoots, which suggested that the thorium-organic complexes did not remain in the roots and were beneficial for thorium transfer from the roots to the shoots. Among three cations (such as calcium ion (Ca²⁺), ferrous ion (Fe²⁺), and zinc ion (Zn²⁺)) in hydroponic media, Zn²⁺had no significant influence on thorium accumulation in the roots, Fe²⁺inhibited thorium accumulation in the roots, and Ca²⁺was found to facilitate thorium accumulation in the roots to a certain extent. This research will help to further understand the mechanism of thorium uptake in plants.

The bioaccumulation of artificial Cs-137 and natural radionuclides Th-234, Ra-226, and K-40 by Basidiomycetes of several species is studied and evaluated in relation to their substratum soils. For this reason, 32 fungal samples, representing 30 species of Basidiomycetes, were collected along with their substratum soil samples, from six selected sampling areas in Greece. The fungal fruit bodies and the soil samples were properly treated and the activity concentrations of the studied radionuclides were measured by gamma spectroscopy. The measured radioactivity levels ranged as follows: Cs-137 from <0.1 to 87.2 ± 0.4 Bq kg⁻¹ fresh weight (F.W.), Th-234 from <0.5 ± 0.9 to 28.3 ± 25.5 Bq kg⁻¹ F.W., Ra-226 from <0.3 to 1.0 ± 0.5 Bq kg⁻¹ F.W., and K-40 from 56.4 ± 3.0 to 759.0 ± 28.3 Bq kg⁻¹ F.W. The analysis of the results supported that the bioaccumulation of the studied natural radionuclides and Cs-137 is dependent on the species and the functional group of the fungi. Fungi were found to accumulate Th-234 and not U-238. What is more, potential bioindicators for each radionuclide among the 32 species studied could be suggested for each habitat, based on their estimated concentration ratios (CRs). The calculation of the CRs’ mean values for each radionuclide revealed a rank in decreasing order for all the species studied.

Biological material itself appears with poor contrast in electron microscopy (EM), due to its composition mostly of light elements. Classical staining agents such as osmium tetroxide, uranyl acetate, and lead citrate preserve and/or stain cellular structures such as membranes, cytoplasm, and organelles well for EM. However, extracellular polymeric substances (EPS) show no or only poor contrast with these staining agents. The endothelial glycocalyx in blood vessels consists mainly of proteoglycans. It can be visualized by EM only by additional staining with heavy metal ions such as copper (Alcian blue, cupromeronic blue), ruthenium (ruthenium red), or lanthanum. Best results are achieved by combined perfusion of fixative and stain. Cationic hydrous thorium dioxide colloids (named here cThO 2 ) trace acidic groups in EPS. We describe here the use of cThO 2 to visualize the glomerular endothelial glycocalyx in the mouse kidney. cThO 2 shows high electron density and binds to a continuous layer of up to a few hundred nanometers thickness on the glomerular endothelium, as well as on epithelia in other blood vessels in perfused animals. The observed staining pattern gives rise to periodic densities, with a spacing varying between 50 and 200 nm, depending on the overall layer thickness, which varies between below 50 up to 300 nm. Due to high electron density of the used cThO 2 particles, the introduced method allows distinct imaging and precise fine structural analysis of the endothelial glycocalyx.

In Polynesia, the complex Society Islands chiefdoms constructed elaborate temples (marae), some of which reached monumental proportions and were associated with human sacrifice in the 'Oro cult. We investigated the development of temples on Mo'orea Island by ²³⁰Th/U dating of corals used as architectural elements (facing veneers, cut-and-dressed blocks, and offerings). The three largest coastal marae (associated with the highest-ranked chiefly lineages) and 19 marae in the inland 'Opunohu Valley containing coral architectural elements were dated. Fifteen corals from the coastal temples meet geochemical criteria for accurate ²³⁰Th/U dating, yield reproducible ages for each marae, and have a mean uncertainty of 9 y (2σ). Of 41 corals from wetter inland sites, 12 show some diagenesis and may yield unreliable ages; however, the majority (32) of inland dates are considered accurate. We also obtained six ¹⁴C dates on charcoal from four marae. The dates indicate that temple architecture on Mo'orea Island developed rapidly over a period of approximately 140 y (ca. AD 1620-1760), with the largest coastal temples constructed immediately before initial European contact (AD 1767). The result of a seriation of architectural features corresponds closely with this chronology. Acropora coral veneers were superceded by cut-and-dressed Porites coral blocks on altar platforms, followed by development of multitier stepped altar platforms and use of pecked basalt stones associated with the late 'Oro cult. This example demonstrates that elaboration of ritual architecture in complex societies may be surprisingly rapid.